Surge protection for photovoltaic systems

The following directives are to be taken into account for standardised surge protection of photovoltaic systems:

• To prevent surge damage, a lightning protection system according to VDE 0185- 305-3 (IEC/ EN 62305-3) is recommended for PV on-roof systems.
• A risk analysis according to VDE 0185-305-2 helps to determine the necessity of a lightning protection system, as well as the required lightning protection class. This only applies for cases in which additional directives, such as the state construction regulations, do not require any other lightning protection systems.
  For complex PV outdoor systems, such as PV power stations or solar parks with the requirement for increased availability, it is wise to check the necessity or requirement for additional measures, taking VDE 0185-305-2 into account.

• Only a protected system can withstand the loads to which it is exposed and safely produce energy over a long period of time. This is why property insurance companies continue to recommend internal surge protection for outdoor PV systems in the new edition of the VdS Directive 2010 (February 2021).
• The standards of the VDE 0100 series, particularly DIN VDE 0100-712, apply to the erection of PV power supply systems.
• If a PV system is newly installed and connected to the electrical system, then surge protection (type 2/Class II) is to be added on the AC side, in accordance with DIN VDE 0100-443 and DIN VDE 0100-712 (IEC 60364-4-44 and 60364-7-712).
• The additional reference to VDE 0185-305-3, Supplementary Sheet 5, in DIN VDE 0100-712 means that, besides the AC side, the DC side also has a requirement for a surge protection system, in order to contribute to the safety of the inverter on systems with an external lightning protection system.

The following points should be particularly observed during the selection:

• The highest open circuit voltage of the PV system may, under no circumstances, exceed the maximum continuous voltage of the surge protection device for the direct current side of the photovoltaic system.
• The number of required protective devices is calculated from the number of MPP trackers in the appropriate PV system.
• If the inverter is connected to information or communication equipment, then these cables should also be included in the equipotential bonding using suitable surge protective devices. 

With PV systems on buildings, the installation of the inverter may be carried out directly on the roof, in the attic or, ever more frequently, in the basement, depending on the local circumstances. In the case of installations in the basement, it can be wise to place the surge protection not only in front of the inverter, but also at the entry of the cables into the building, in order to avoid inductive couplings from outside.

Surge protection for PV systems always has two sides: Both on the direct current side and on the alternating current side, surge voltages can be coupled into the system for all kinds of reasons, for example, and can damage the inverter. OBO surge protection reliably protects every side. To protect the DC-side input of the inverter, OBO offers a portfolio of generator connection boxes with lightning and surge protection. 

Learn more.